plan vs undirected graph

plan

noun
  • A two-dimensional drawing of a building as seen from above with obscuring or irrelevant details such as roof removed, or of a floor of a building, revealing the internal layout; as distinct from the elevation. 

  • A drawing showing technical details of a building, machine, etc., with unwanted details omitted, and often using symbols rather than detailed drawing to represent doors, valves, etc. 

  • A subscription to a service. 

  • A set of intended actions, usually mutually related, through which one expects to achieve a goal. 

  • A method; a way of procedure; a custom. 

verb
  • To create a plan for. 

  • To intend. 

  • To design (a building, machine, etc.). 

  • To make a plan. 

undirected graph

noun
  • A graph in which the edges are not ordered, so the edge (a, b) is identical to the edge (b, a). 

How often have the words plan and undirected graph occurred in a corpus of books? (source: Google Ngram Viewer )